CVE-2026-55574: vllm-project vllm

Vulnerability summary

CVE-2026-55574 is a high (CVSS 8.7) vulnerability in vllm-project vllm. EPSS estimates a 0.58% chance of exploitation in the next 30 days, higher than 46.8% of scored vulnerabilities.

Timeline

1. 06-07-2026
   PublishedVulnerability first disclosed.
2. 06-07-2026
   Last modifiedVulnerability information updated.

Description

vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, the structured_outputs.regex API parameter passes a user-supplied regular expression string directly to the grammar compiler backends with no compilation timeout; in the xgrammar backend the string reaches the regex compiler with no guard, and in the outlines backend the validation step blocks structural issues such as lookarounds and backreferences but performs no complexity analysis, so a pattern with nested quantifiers passes all checks and causes exponential state-space expansion, allowing a single request containing an adversarial regex to hang an inference worker indefinitely and deny service. This issue is fixed in version 0.24.0.

• CWE-1333Inefficient Regular Expression ComplexityThe product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.